Individuals who remain seated for an extended period of time may develop symptoms of muscle fatigue and blood circulation problems. It is known that such muscle fatigue and circulation problems may be relieved, in part, by a lumbar support whose position is adjustable along a guide track.
Conventional adjustable lumbar support systems typically employ a mechanical adjusting means or a motor and gearbox assembly, commonly referred to as actuators, as an adjusting means. A four-way power lumbar support system may provide a level adjustment in a vertical direction and an arching adjustment of a flexible, resilient support element in a horizontal direction toward and away from a seat occupant. Such a system requires two separate actuators, that is, one for each adjustment direction.
Conventional variable lumbar support devices have generally included two traction cables for applying the force of the actuators to the lumbar support. Bowden cables are commonly used as traction cables for such devices. Lumbar supports employing Bowden type or other traction cable assemblies as part of a means for adjusting the lumbar support in a seat are known. Bowden or traction cables are coaxial mechanical devices wherein a wire slides axially through a sleeve or conduit. Traction cables have been found to be an efficient means for applying traction to moving parts of a lumbar support.
It is known to anchor a traction cable sleeve end to one part of the lumbar support device and to anchor the traction cable wire end to another part of the movable lumbar support device. When so anchored, drawing the traction cable wire through the traction cable sleeve causes the moving parts of the lumbar support device to travel from a relaxed, substantially flat and non-supporting position to a tensioned, supporting position such as a bowed arch. In the more expensive lumbar support systems, traction is applied via an electric motor, which acts on the end of the traction cable opposite the lumbar support device to draw the wire of a traction cable through the sleeve of the traction cable. For devices to be installed in more economical seats, mechanical actuators are used.
Prior art devices are known which provide lumbar supports that are slidable along a guide track. The support elements may be rigid or flexible. In some of these prior art devices, a traction cable is used to apply force to the support member for adjustment of the support member in one direction. Such an arrangement in conventional lumbar support systems has typically required the use of a spring to counteract the force of the traction cable, to bias the support member towards a rest position and to apply force to the support member in the return direction. Use of a spring to counteract the force of the traction cable is disadvantageous because overcoming the spring requires higher operating forces for the lumbar support system.
Such devices include several other drawbacks and limitations as well. Many of the commonly used adjustable lumbar support devices are composed of a relatively large number of parts. This is problematic because it renders these types of devices difficult to manufacture, package and assemble. Weight and expense are increased. Furthermore, these relatively complex conventional lumbar support devices are expensive to manufacture and may be unreliable and prone to breakdown. More powerful motors are required to overcome the forces of the springs, further increasing weight and expense. In mechanically actuated devices, complicated linkages become necessary to overcome the spring force.
Highly competitive markets for automobile seats and furniture place a premium on optimization of weight, cost and durability. There is a need in the industry for reducing the complication of assemblies, reducing packaging size, reducing cost and increasing durability. Accordingly, the need exists to provide an improved power lumbar support system that is cost-effective and light weight, yet still provides the quality of performance equal to that of conventional lumbar support systems.